Olelo
From Organic Design wiki
Olelo, or Git-Wiki, is a wiki that uses git to manage pages. Olelo is written in Ruby and uses the Catalyst MVC web framework.
Git-Wiki stores the pages in a git repository. Therefore you can use all the benefits of the revision control software (distributed content etc). Multiple markup languages are supported via plugins. The wiki has a very extensible architecture. Custom markup can be added via filters. Additional tags can be added (e.g. the math tag which is provided for LaTeX-rendering).